In a water bag or a balloon toy made of a plastic film or rubber, a fluid such as gas or a liquid is conventionally sealed hermetically in various ways. In one way, a tube of a predetermined length extending from the main body of a water bag or a balloon toy, may be bound at its projecting portion after the main body has been filled with a fluid through the tube, thereby to prevent the fluid from leaking from the main body. In another way a check valve is mounted on a passage port of the main body. The sealing of the check valve prevents a fluid filled in the main body from leaking therefrom.
The former means not only requires a troublesome tube binding operaton, but also presents the defect that a portion of the fluid filled in the main body easily leaks during the tube binding operation. The latter means presents the defects that the valve itself has a very complicated structure and requires special structural members and much labor for attachment of the valve, resulting in expensive costs. Moreover, such valve may easily be damaged during the use, thereby to lower or lose the sealing function as a check valve.